Cascade washing apparatus



1966 R. LEONARD ETAL 3, 30,747

CASCADE WASHING APPARATUS Filed Sept. 15, 1963 FIG.|

INVENTORS R.L. LEONARD T. B. TRUSCOTT T. M. VEAZEY 32mg MA ATTORNE.

United States Patent F 3,230,747 CASCADE WASHING APPARATUS Richard L.Leona d; Thomas B. Truscott, and-Thomas M.

Veazey, Decatur, Ala., assignors t0 Monsanto Company, a corporation ofDelaware Eiled'Sept. 1 3, 1963, Ser. No. 398,883 1 Claim. (l. 68-43) Thepresent invention relates to the washing of synthetic fibers and morespecifically to the stripping of a tow as it pases along a cascade.

In the wet spinning process of making synthetic fiber, a dope whichconsists of a polymer and a solvent is extruded through spinnerettesintoa coagulation bath to form a filamentary tow. The two is then washrelatively free of solvent by hot water traveling down a cascade as thetow is being drawn up the cascade. In order for the tow to be of anacceptable qua-ilty, it must be washed until it is almost completelyfree of solvent. The wash water clings to the tow forming a boundarylayer of water which impedes the rinsing process. This boundary layer isremoved in the present invention by stripping the tow. The tow can bestripped by being sharply bent or by being nipped. When the tow is beingdrawn up the cascade, it is impractical to bend it, therefore a methodof nipping the tow is employed. Accordingly, a primary object of thisinvention is to provide a cascade with a stripper which will effectivelyremove the boundary layer of wash water from the tow and permit freshwash water to rinse the tow thereby removing the undesirable solvent.

Another object of this invention is to provide a cascade with a stripperwhich has a pivotally mounted depressor bar.

A further object of this invention is to provide a cascade with astripper which forms a weir.

A still further object of this invention is to provide a cascade with astripper which removes the boundary layer of water from the tow and alsoguides and aligns the tow.

FIGURE 1 of the drawings isometrically shows a section of the cascade inwhich a stripper is employed.

FIGURE 2 is a sectional view of the apparatus demonstrating particularlythe pivoting movement of the depressor bar and the boundary layer washwater being stripped from the tow.

One embodiment of the present invention contemplates using a depressorbar to force the tow against a stripper bar which removes the boundarylayer of wash water from tow thereby more eificiently rinsing thesolvent from the tow. After the dope is extruded from the spinneretteand coagulates forming the tow, it is then drawn up the cascade wherethe wash water removes the undesirable solvent. The tow is drawn betweena stationary stripper bar and a pivotally mounted depressor bar. Thedepressor bar pivots through an arc and forces the tow against thestripper bar. The tow is put under a slight compression and by thefriction which is produced between the tow and the stripper bar and thetow and the depressor bar, the boundary layer of water clinging to thetow is stripped. By removing the water forming the boundary layer, thetow can proceed to the next section of the cascade with a reducedsolvent concentration. The tow after proceeding between the depressorbar and the stripper bar comes in contact with water backed up by a weirwhich is formed by the depressor bar and the stripper bar. This backupwater through its turbulence swirls around the tow and continues to washthe sol-vent therefrom. This method of nipping the tow is repeated asufficient number of times along the length of the cascade to reduce thesolvent content in the tow to an acceptable level.

The stripper bar is not an absolutely necessary element of the inventionand the boundary layer wash water can 3,23%,747 Patentedv Jan. 25',1966:

be nipped without it but to properly align the tow and to keep the towfrom rubbing against the bottom of the cascade, the stripper bar is avery desirable element;

Referring now to the drawings, the wet spinning apparatus andcoagulating hath (not shown) have prepared the tow 10, which is thefiber to be washed, to be drawn up the cascade 11'. The cascade 11extends from the coagulating bath to the drying apparatus (not shown).Relatively pure wash water 12 is supplied .at the upper end of-th-ecascade 11 and is gravity forced down the length of the cascade 11 whereit is then drained off. The cascade 11 is in the shape of a troughhaving a bottom panel 13 and sides 14 and 15' parallel to each other andperpendicular to the bottom panel 13.

Depressor bar guides 16 and 17 are rigidly secured to the top of sides14 and 15 respectively, the depressor bar guides 14 and 15 beingprovided with slots 18- and 19 which are adapted to receive a pivotingbar 20. The pivoting bar 20 is integrally connected with a depressor barshaft 21 which is perpendicular to pivoting bar 20 and the depressor barshaft 2 1 is integrally connected with a depressor bar nipper 22' whichis perpendicular to the depressor bar shaft 21 and parallel to pivotingbar 20. The depressor bar guides 16 and 17 permit the pivoting bar 20 tofreely rotate thereby permitting the depressor bar nipper 22 to pivotabout an axis which is parallel to its longitudinal dimension.

The stripper bar 23 is rigidly secured to and is per-pendicular tocascade sides 14 and 15. The depressor bar nipper 22 is parallel to andrests on the stripper bar in the absence of tow 10. When the tow 10 isdrawn up the cascade 11 and between the stripper bar 23 and thedepressor bar nipper 22 depressor bar nipper 22 contacts the tow 1t) andimpinges it against the stripper bar. When the tow 10 touches thestripper bar 23 and the depressor bar nipper 22, the water forming theboundary layer 25 around the tow 10 is broken and is thereby dissipatedallowing the wash water 12 to make new contact with the tow 10. Forevery set of stripper bars and depressor bar nippers, this method ofstripping the boundary layer water is repeated thereby permitting thewash water to properly rinse the tow and remove the solvent containedtherein.

The stripper bar 23 and the depressor bar nipper 22 form a weir whichbacks up the wash water 12. As the wash water 12 spills over thedepressor bar nipper 22, it produces a turbulence in the back water 24which helps circulate the wash water 12 around the tow 10 and therebyaids in the rinse.

It is to be noted that the stripper bar 23 and the depressor bar nipper22 also aid in effecting a better rinse by reducing the concentration ofthe wash water that forms the boundary layer. By stripping the tow 10,the boundary layer wash water 25 with its high concentration of solventis prohibited from mixing with the back water 24- which has a lowerconcentration of solvent. The amount of solvent removed from the tow 11by each strip-per can be mathematically illustrated by letting Xrepresenting the concentration of the solvent in the tow 10 beforeentering the stripper and letting X represent the concentration of thesolvent in the tow 10 after it has been nipped, therefore, X, thequantity of solvent removed by each stripper, can be determined by theformula X =X X The value of X is the quantity of solvent that eachstripper prevents from mixing with the wash water on the back water sideof the weir. Since the wash water 12 has less solvent intermixedtherein, the solvent can be more effectively removed from the tow 10.

The depressor bar nipper 22 by pressing the tow 10 against the stripperbar 23 aligns the tow 10 and keeps it from floating to the surface ofthe wash water 12. This alignment assures a proper rinse by keeping thetow submerged and by uniformly collimating the tow 10 as it travels upthe cascade 11.

While a preferred embodiment of the invention has been disclosed, it isto be understood that changes and variations may be made withoutdeparting from the spirit and scope of the invention as defined by theappended claim.

We claim:

Apparatus for continuously stripping the washing fluid forming aboundary layer on the surface of a tow consisting of a bundle offilaments of synthetic material comprising:

(a) a cascade having a bottom portion and side portions secured theretoto thereby form a trough for a Washing fluid;

(b) an elongated smooth surface cylindrical stripper bar mounted in saidcascade and extending between said side portions;

(0) a pair of oppositely disposed, slotted bar guides each mounted on aside portion above said stripper bar;

(d) an elongated bar rotatably and removably mounted in said slots withits axis of rotation passing through said slots and extending acrosssaid trough;

(e) a depressor bar shaft secured to and revolvable with said elongatedbar about said axis;

(f) a smooth surfaced nipper bar secured to and revolvable about saidaxis with said depressor bar shaft and said elongated bar;

(g) said bar guides and said stripper bar being so related to oneanother that an arc passing through a point on said nipper bar andhaving its center coincident vvith said axis of rotation of saidelongated bar will also pass through said stripper bar whereby pressurewill be applied to a tow moving between and contacting the stripper barand nipper bar, and the boundary layer of washing fluid thereby strippedtherefrom.

References Cited by the Examiner UNITED STATES PATENTS 2,133,535 10/1938Campolunghi. 2,516,268 7/1950 Spalding 68175 2,665,189 1/1954 Cox 68205X 2,782,623 2/1957 Coe 68-181 FOREIGN PATENTS 661,941 4/1963 Canada.

25 IRVING BUNEVICH, Primary Examiner.

